1. Field of the Invention
The inventions disclosed and taught herein relate generally to a precision cooling systems for heat generating objects; and more specifically to an improved heat exchanger for use in precision cooling systems for high density heat load environments.
2. Description of the Related Art
Many new computer and electronic system designs combine multiple heat-producing components, such as microprocessors or processor boards, in an enclosed environment. Supercomputers and other large computer systems typically include a large number of processors housed in cabinets or racks. Due to the demand for more components in increasingly smaller spaces, computer and electronic systems are increasingly configured and designed to be closer together, and many existing cooling systems for these electronic systems may not provide adequate heat removal.
At the same time, newer, more powerful electronic components are constantly being introduced. With this higher performance, these new components typically have significantly increased heat generation. Thus, these new components are driving up the heat production of new computer and electronic designs to the point where traditional heat cooling methods may not provide enough cooling capacity to these new systems to operate at their designed conditions in close-packed, enclosed spaces, such as rack enclosures. As a result, these newer, more powerful, high heat-producing systems may have to operate at reduced performance levels to limit the heat generation. Further, some locations in a computer cabinet, rack or other electronic system may be hotter than others during operation of the system because there may be a density of components and/or poor positioning with respect to the flow of cooling air.
Typical cooling systems for electronic and computer systems, such as rack enclosures, include simply drawing ambient air over the electronic components to cool them. In this cooling solution, many of the components receive warmer air than other components because the air has already passed over and absorbed heat from other components. Consequently, some components may not be adequately cooled. Also, these types of systems usually dumped the removed heat load into the general environment, such as a computer room, which may overload the environmental cooling system.
Other cooling systems have used heat exchangers to transfer heat from the air to a fluid, for example, water or refrigerant, contained in the heat exchanger. In these systems air is passed over the heat exchanger and heat is transferred to the fluid in the heat exchanger and then removed from the system. Systems may differ as to whether the air entering the enclosure or system is cooled prior to flowing across the heat-producing components, or whether the air exiting the enclosure or system is cooled after having removed heat from the components, or both.
Air-to-fluid heat exchanger systems may utilize a single phase fluid, such as chilled water, or a multi-phase fluid, such as a conventional two-phase refrigerant. Multi-phase fluid systems may include a conventional vapor compression system in which a gas is compressed to allow heat rejection at higher outdoor temperatures, or a pumped system in which heat is rejected to a lower temperature. In both systems, the temperature and pressure of the fluid are controlled so that the heat to be removed causes the fluid to boil, thereby absorbing heat. In this regard, the disclosure and teaching of co-pending application Ser. No. 10/904,889, entitled Cooling System for High Density Heat Load, which was published on Jun. 9, 2005, as Publication No. 2005/0120737; and co-pending application Ser. No. 11/164,187, entitled Integrated Heat Exchangers in a Rack For Vertical Board Style Computer Systems, which was published on May 18, 2006, as Publication No. 2006/0102322, are incorporated by reference herein for all purposes.
To effectively cool the ever increasing heat densities with conventional systems, typical solutions to increase the heat transfer rate include increasing the flow of refrigerant through the cooling system and/or increasing the flow of air across the heat exchanger. However, in pumped and vapor compression refrigerant systems, the temperature at which the fluid begins to boil is determined by, among other things, the pressure drop across heat exchanger. As the pressure drop across the heat exchanger increases, the temperature at which the refrigerant in the heat exchanger boils also increases. A higher refrigerant evaporation temperature in the heat exchanger may lead to a decrease in the overall cooling capacity of heat exchanger because the temperature difference between the heated air and refrigerant evaporation temperature decreases, and the system is not able to remove as much heat from the air. In addition, increased flow rate of fluid through a heat exchanger tends to increase the pressure drop across the heat exchanger.
The inventions disclosed and taught herein are directed to precision cooling systems for high density heat loads including an improved heat exchanger for use in precision cooling systems for high density heat load environments.